A great number of chemical substances having a herbicidal activity have been used for herbicidal agents to exterminate or control the vegetation of undesired weeds in agricultural and non-agricultural fields. However, there are many kinds of weeds and their growth extends over a long period of time, so that most of the conventional herbicidal agents have an effect only on the specific kinds of weeds. Accordingly, there is a great demand on herbicidal agents capable of exerting a strong herbicidal activity against a wide variety of weeds without any material phytotoxicity to crop plants.
By the way, no-till cultivation has recently been developed for saving labor work, extending a cultivation period and preventing loss in weight of soil. For this reason, there also is a great demand on herbicidal agents capable of exerting a distinct herbicidal activity in foliar treatment, maintaining a prolonged herbicidal efficacy in soil treatment and showing a prominent selectivity between crop plants and weeds.